1. Field of the Invention
Methods consistent with the present invention relate to providing initial pictures to digital television (TV), and more particularly, to providing initial pictures to the screen of a digital TV in a network that supports isochronous data communications.
2. Description of the Related Art
Digital broadcasting offers a better picture quality and clearer sound than conventional analog broadcasting. In digital broadcasting, audio and video data is transmitted over electronic waves and then is displayed on the screen of a digital TV in a digitalized manner. In other words, in digital broadcasting, all necessary operations, including modulation and demodulation of digital broadcast programs, are carried out in a digitalized manner. Thus, digital broadcasting is less affected by noise than analog broadcasting.
In addition, digital broadcasting can provide much more broadcast channels than analog broadcasting. In digital broadcasting, a plurality of programs can be transmitted using a single bandwidth, while in analog broadcasting, only one program can be transmitted using a single bandwidth of about 6 MHz. It is audio and video compression that has enabled such digital multi-channel broadcasting. In existing digital broadcasting techniques, broadcast programs are compressed using a Moving Picture Experts Group (MPEG)-2 transport stream (TS) format for transmission. In addition, digital broadcasting supports multi-channel sounds, for example, 5.1 channel sounds, and thus, when watching TV at home, a user can enjoy an acoustic effect equal to or approximate to the acoustic effect of a movie theater.
In order to receive a digital broadcast program, a digital broadcast receiver called a set-top box is needed. A digital broadcast receiver and a digital TV may be sold together or separately.
FIG. 1 is a diagram illustrating a digital broadcast receipt system 100.
Referring to FIG. 1, the digital broadcast receipt system 100 includes a TV 120, which is a regular TV, and a conventional set-top box 110. The conventional set-top box 110 receives a digital broadcast, reconstructs analog audio and video from the digital broadcast, and transmits the reconstructed analog audio and video to the TV 120. The digital broadcast transmitted to the conventional set-top box 110 may be classified into a digital terrestrial broadcast, a digital cable broadcast, or a digital satellite broadcast. A digital terrestrial broadcast can be received using an antenna (not shown), a digital satellite broadcast can be received using a satellite broadcast receiving antenna (not shown) having a parabolic surface, and a digital cable broadcast can be received using a coaxial cable 160. The conventional set-top box 110 receives digital broadcast programs in a desired bandwidth, which are multiplexed as MPEG-2 transport streams (TSs). Through tuning, the set-top box 110 demultiplexes the digital broadcast programs, and extracts video and audio data of a digital broadcast program selected by a user from the demultiplexed digital broadcast programs. Since the extracted video data is compressed in MPEG-2 format, the conventional set-top box 110 reconstructs video signals from the extracted video data by decoding the extracted video data with the use of an MPEG-2 decoder (not shown) installed therein. In addition, since the extracted audio data is compressed in AC-3 or DTS format, the conventional set-top box 110 reconstructs 5.1 channel audio signals from the extracted audio data by decoding the extracted audio data. The reconstructed video and audio signals are analog signals to be transmitted to the TV 120.
The conventional set-top box 10 and the TV 120 are connected to each other via an analog/video (A/V) cable 150. Therefore, the TV 120 can receive signals from the conventional set-top box 110 via the A/V cable 150. The TV 120 receives analog signals from the conventional set-top box 110, outputs the received analog signals as visible rays using a Braun tube, a plasma display panel (PDP), or a liquid crystal display (LCD). In addition, the TV 120 receives audio signals from the conventional set-top box 110 and outputs the received audio signals using a speaker.
FIG. 2 is a diagram illustrating a digital broadcast receipt system 200. Referring to FIG. 2, the digital broadcast receipt system 200, unlike the digital broadcast receipt system 100 of FIG. 1, includes a digital TV 220. Accordingly, a conventional set-top box 210 included in the digital broadcast receipt system 200, unlike the set-top box 110 of FIG. 1, does not need to reconstruct video and audio signals from the compressed video and audio data by decoding the compressed video and audio data. The set-top box 210 receives digital broadcast programs, which are multiplexed as MPEG-2 TSs, in one of a plurality of bandwidths using a tuner (not shown), demultiplexes the digital broadcast programs, and extracts video and audio data of a digital broadcast program selected by a user from the demultiplexed digital broadcast programs.
When extracting video data, audio data, and other data of the selected digital broadcast program, the set-top box 210 uses physical identifiers (PIDs), which are numbers allotted to video data, audio data, and other data transmitted from each broadcasting station. For example, supposing that PIDs 3, 7, and 8 are allotted to video data, audio data, and other data (such as subtitles), respectively, of a broadcast program on channel 24, the conventional set-top box 210 extracts the broadcast program on channel 24 by extracting only data designated by the PIDs 3, 7, and 8 from input digital broadcast signals. The extracted broadcast program comprised of video data, audio data, and other data is transmitted to the digital TV 220 as digitalized data via a network cable 250.
Various digital devices can be connected to the digital TV 220 and the conventional set-top box 210, which are connected to each other via the network cable 250. For example, as shown in FIG. 2, a digital camcorder 230 and an audio player 240 may be connected to the digital TV 220, in which case, the digital TV 220 can display pictures received from the digital camcorder 230 on its screen or can output audio signals transmitted thereto using the audio player 240.
Initialization of a digital TV to which various digital devices are connected in a network will now be described in detail with reference to FIG. 3. Referring to FIG. 3, in operation S310, if the digital TV is in a power-off mode or standby mode, a user issues a command to turn on or activate the digital TV using a user interface, such as a control button attached on the digital TV or a remote controller, so that the digital TV is turned on or activated.
In operation S312, the digital TV recognizes devices connected to it in a network through a discovery operation, such as a set-top box. In operation S314, the digital TV sets up the set-top box. The setup of the set-top box involves identifying a current state of the set-top box and setting parameters in the set-top box necessary for operation of the set-top box. For example, if the set-top box is turned off or stands by, parameters necessary for turning on or activating the set-top box are sent to the set-top box. If the set-top box has already been activated, the sending of the parameters necessary for activating the set-top box may be skipped.
After initial operations, i.e., operations S310, S312, and S314, the user issues a command to select a main menu using the user interface in operation S320. Then, the digital TV displays the main menu on its screen.
In operation S322, the user selects the set-top box using the main menu in order to watch a digital broadcast program via the set-top box. If the set-top box is selected, the digital TV displays menus for controlling the set-top box on its screen.
In operation S324, the user selects a channel using a channel selection menu, which is one of the menus for controlling the set-top box. The user may select a desired channel by directly inputting a channel number corresponding to the channel into the digital TV or by checking up a plurality of channels provided by an electronic program guide (EPG) and then selecting one of the channels.
The EPG is provided to the digital TV through broadcasting via the set-top box. If the user selects the channel of interest in operation S324, the digital TV sends channel information of the selected channel to the set-top box and issues a request for sending a broadcast program of the selected channel to the set-top box.
In operation S330, the set-top box sends the requested broadcast program to the digital TV as MPEG-2 TSs, and the digital TV receives the MPEG-2 TSs sent by the set-top box. In operation S332, the digital TV obtains video and audio signals and other data by decoding the received MPEG-2 TSs.
Conventionally, the user is required to perform at least three operations for manipulating a digital TV, i.e., operations S320, S322, and S324, to watch a broadcast program, which is very inconvenient. In order to solve this problem, an IEEE 1394-based digital AV networking initiative dubbed HAVi (Home Audio Video interoperability) (www.havi.org) has been suggested. HAVi alleviates a user's inconvenience by enabling the digital TV to memorize a device that it most recently accessed before being turned off, such that it automatically accesses the device ahead of other devices as soon as it is turned on. However, this type of method may cause problems especially when devices are disconnected from an IEEE 1394-based network. For example, referring to FIG. 2, if the digital TV 220 is turned off while displaying pictures received from the digital camcorder 230 and then a user disconnects the digital camcorder 230 from a network, no picture is displayed on the screen of the digital TV 220 when the digital TV 220 is turned on. In other words, when the digital TV 220 is turned on, it attempts to search for the digital camcorder 230 through a discovery operation because the digital camcorder 230 is the device that it had most recently accessed. However, the digital camcorder 230 does not exist any longer in the network. Therefore, the digital TV 220 cannot receive any video signals from the digital camcorder 230. Therefore, the digital TV 220 does not display any initial pictures on its screen.